Hierarchial access for DUT signals

How do we hierarchially access the signals internal to DUT?
I had used the syntax: $root.<tb_top>.<dut_inst>.<dut_subblock>.signal
but I got the error
** Error: : (vlog-7027) Hierarchical reference not allowed from within a package.
Please suggest me a way to do the same.

I vaguely recall Questa older version (6.5a --) used to throw similar error, but got fixed in later releases. Which version are you using?

If you can show a full testcase it is lot easier to point out. Try mimicking it with XBUs or so.

Srini
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